Having issues with Low Poly Texture Colours
you probably have too high the specularity of the material, what I'm showing you is an example in blender render, I'm not a render professional, my area is programming, but I've been studying for almost 4 years and today I work with shading language, and I'm still using BGE.

in conclusion you have to lower the specularity of the material so that it does not seem like it is going beyond the spaces of your color palette


I made my palette with 128 X 128 px squares
use unwrap view project, with the View Ortho 1
from the leaves of the trees select some faces from my unwrap and place them in another color to contrast


if you need to expand this answer, just say uqe more you want to know to include it in the answer